Abstract

Aim

Around 30% of non-small cell lung cancer (NSCLC) patients present LM during the disease course causing a negative clinical impact on survival and quality of life. The expression of certain genes in cancer cells and also TME gene expression might be crucial for allowing tumor cells to spread to the liver. According to this hypothesis Id1 and Id3 genes, part of the signature that facilitates breast cancer cells to disseminate to the lungs, might be determinant for NSCLC LM development.

Methods

First we validated Id1 as a significant and independent prognostic factor among patients with adenocarcinoma of the lung. Recently, we have communicated the development of a mouse model of LM from lung cancer in which the only absence of Id1 expression in TME of Id1-knockout (KO) animals was sufficient to avoid LM formation by 50%. Now we aimed to evaluate the additional impact of Id1 and Id3 genes deficiency in tumor cells on LM generation. Therefore, 2 cohorts including 23 mice were compared; Id1 wild-type (WT) female mice (n = 12) vs. KO female animals (n = 11). In both groups of mice 500,000 Lewis Lung Carcinoma cells (LLC) either Id1 homozygously deficient (Id1-/-) and Id3 WT (Id3 + /+) or Id1-/- and Id3 heterozygously deficient (Id3 + /-), generated through gene silencing, were intrasplenically injected. Thereafter, both groups of mice were weekly monitored with FDG-micro-positron emission tomography scans (mPET) for LM formation. Animals were sacrificed (and tissues microscopically analyzed) by the time LM were developed and clinical deterioration was evident, according to our Animal Ethics Committee approved protocol.

Mice genotype

Positive PET at week 2

p value

WT

41.7%

KO

0%

0.02

Microscopic LM at necropsy

WT

83.3%

KO

36.4%

0.03

Results

LM were significantly more likely to appear among Id1 WT mice compared to Id1 KO mice with a relative risk of 2.29 (IC95% 1.01-5.22). Results are summarized in Table 1

Conclusions

In this model, the absence of Id1 in TME of KO mice in combination with the lack of Id1/Id3 expression in intrasplenically injected lung cancer cells showed to be a more significantly efficient strategy to prevent LM formation.